The voltage error integrator regulates the output voltage by adjusting the current control voltage, VSHARE, similar to any current mode control architecture. A transconductance amplifier compares the sense feedback voltage to a programmed reference voltage to set the current control voltage VSHARE to maintain the desired output voltage. While a regulated current source feeding an output capacitance provides a natural, stable integrator, mid-band gain is often desired to improve the loop bandwidth and transient response.

With a transconductance set by the current sense gain, the voltage loop cross-over occurs when the full loop gain equal 1 according to Equation 6.

Equation 6.

To prevent the current integration loop bandwdith from negatively impacting the phase margin of the voltage loop, the voltage loop must have a target bandwidth of Fcoi / 2.5. With a current mode loop of f_SW/4, the voltage loop mid-band gain must be Equation 7:

Equation 7.

An integrator pole is necessary to maintain accurate DC regulation, and the zero-frequency set by RVV × CZV must be set below the lowest cross-over frequency with the largest output capacitor intended to be supported at the output, but not more than 1/2 the target voltage loop crossover frequency f_cov.

A high frequency noise pole, intended to keep switching noise out of the current loop must also be employed, with a high-frequency pole set by RVV × CPV must be set between f_sw/4 and f_sw.

For pin programmed options of compensation components, see Table 7-9.

For PMBus programming of compensation values, see (B1h) USER_DATA_01 (COMPENSATION_CONFIG).